TW593209B - Porous silicon nitride ceramics and method for producing the same - Google Patents

Abstract

The invention provides porous silicon nitride ceramics that have uniform, fine closed pores and a manufacturing method thereof. Metal Si powder is mixed with a sintering additive, followed by thermal treatment, which is a pre-process for forming a specific grain boundary phase. Two-stage thermal treatment is thereafter performed by microwave heating at a temperature of 1000 DEG C or more. The metal Si powder is thereafter subjected to a nitriding reaction from its surface, the metal Si is thereafter diffused to nitride formed on the outer shell of the metal Si, and thereby porous silicon nitride ceramics that have uniform, fine closed pores can be obtained. Since the porous silicon nitride ceramics of the present invention have a high ratio of closed pores and are superior in electrical/mechanical characteristics, excellent characteristics can be displayed if they are used, for example, for an electronic circuit board that requires an anti-hygroscopicity, a low dielectric constant, a low dielectric loss, and mechanical strength.

Description

A7 ________ Β7 V. Description of the invention () The technical field of the invention, X month is related to the use of dielectric materials such as various wiring circuit boards, insulating materials or radio wave transmission materials, or porous nitrogen with light moisture-resistant structural materials Siliconized ceramics and methods of making them. Prior art Ceramics are used as materials for various structural materials or electronic component materials. In recent years, they have been eager for light weight and high strength, or improved electrical characteristics. For example, in order to reduce the weight of the table material used for high-accuracy 'return speed drive', such as wafer transfer table or drawing table used for components of material manufacturing equipment, etc. With the recent increase in frequency of circuit substrates and insulating materials used in such applications, materials with lower dielectric constant and lower dielectric loss are strongly demanded. -For this reason, it is believed that it is effective to use ceramics as porous materials. For example, if the relative rigidity of ceramics is reduced by 50%, this weight can be reduced, and the dielectric constant shown by air is about 〖, and the dielectric loss is Because of its excellent electrical insulation properties of 0, porous ceramics are expected to be materials with low dielectric constant and low dielectric loss. However, it is difficult to obtain a porous sintered body in which fine pores are uniformly dispersed only by controlling the sintering step of the ceramic sintered body. Generally, the occurrence of coarse pores causes problems such as decreased strength or uneven characteristics. In addition, since the pores of the obtained porous sintered body are almost pores, the original moisture resistance of the ceramic is impaired, the electrical characteristics (dielectric rate, and dielectric loss) of the moisture are significantly deteriorated, or variations in various characteristics, etc. However, there is a problem that the characteristics cannot be expected practically. 000317 This paper is sized for China National Standard (CNS) A4 (210X297 mm) 593209 A7

593209 A7 ---__ B7 V. Description of the Invention (Q) Questions that take more effort. Japanese Patent Application Laid-Open No. 1 1-1 16333 discloses that the heat-treated borosilicate glass is phase-separated to dissolve the soluble phase. After pulverization, it is melted with flame only on the surface, and it can be adjusted to have a nanometer level by closing the porosity. A method for producing a ceramic circuit board using a closed-cell porous glass m glass porous heat treatment obtained by crystallization heat treatment, adjusting a glass / aggregate material / resin ball mixture, and a method of making μ. The specific dielectric constant of the circuit board obtained by this method is less than 2 and the coefficient of thermal expansion is 13 to 17 ppm / t :. In this method, the materials are separated by heat treatment to define a material that dissolves the soluble phase. χ, not only the manufacturing process is complicated, but it is necessary to use compounding in heterogeneous phases. The original mechanical and electrical characteristics are not obtained. Moreover, once the open pores are surrounded, it will be difficult to completely dissociate due to moisture absorption. The problem of control arises. In the conventional technique for forming the closed pores as described above, it is necessary to add a second phase different from the foaming agent or the melt or a base material phase with a coefficient of thermal expansion that is different. Because of the residue of the second phase or the second phase, However, there will be a significant reduction in electrical and mechanical characteristics. In addition, if the porosity is too large, the matrix of the base material cannot be formed, the pore size cannot be controlled, etc., and the porosity and pore size formed will be limited. Problems to be Solved by the Invention The present invention is to provide a solution to the above-mentioned problems. That is, the present invention is a porous silicon nitride ceramic having uniform and fine closed pores and a method for producing the same. The porous silicon nitride ceramic of the present invention has a relative density of less than 70/0, a closed pore ratio in the whole pores of 50% or more, and more preferably, a relative density of less than 50%, and the closed pores in the full pores. The ratio is above 90%.

This paper size applies to China National Standard (CNS) A4 (210 X 297 mm) 593209 A7 B7

V. Description of the invention (4 In the case of porous ceramics, the porous silicon nitride ceramics of the present invention have hollow particles as shown in the pattern. Structure, the dense part (backbone) is a continuous network structure, and because it does not contain coarse pores, it has better mechanical strength and electrical characteristics than conventional porous ceramics, especially because the particles become hollow. Therefore, in the porous ceramics with uniform structure of the pores with a dispersed diameter, in any section of the porous ceramics, there can be between the two adjacent pore radii rl, ^ and the width b of the Taoman part. The relationship (1 ^ + r2) / b> i is preferably + r2) / b > 2. The porous silicon nitride ceramic of the present invention contains a crystal phase of an oxynitride or a silicon oxynitride compound represented by RE4Si2N207 or RE1GN2 (Si〇4) 6. It is a ceramic circuit board characterized in that at least a part of the insulating layer is made of the porous ceramic material. In addition, the porous silicon nitride ceramic of the present invention is a metal powder containing at least Yb, Sm or Er! This kind of powder is equivalent to those having a powder content of 2 to 25 moles. After forming the molded body, it is produced by a heat treatment manufacturing method in a surrounding gas containing nitrogen. Furthermore, the above-mentioned formed body is subjected to thermal treatment under microwave or millimeter irradiation 'to obtain a porous silicon nitride ceramic from hollow silicon nitride ceramic particles. BRIEF DESCRIPTION OF THE DRAWINGS (Description of Element Symbols) FIG. 1 is a schematic diagram of a sectional structure of a porous ceramic according to the invention of the present application. FIG. 2 is a schematic diagram of a cross-sectional structure of a conventional porous ceramic. Fig. 3 shows the sintering process of the porous ceramic according to the present invention. It is a formed state '(b) is an initial state of sintering, and (c) is a state of being sintered. Γ Ρ ο ο ο η The paper size applies to China National Standard (CNS) A4 (210 x 297 mm)

Line 593209 A7 ___B7 V. Description of the invention (5) Figure 4 shows the change pattern of metal particles during the sintering process of the porous ceramic of the present invention, (a) is the state before sintering, and (b) is sintering The initial state (c) is a state in which sintering is progressing and a state in which sintering is completed. Embodiments of the invention: The porous silicon nitride ceramics of the present invention is produced by the following cross formula in detail. The porous silicon nitride ceramic of the present invention includes a step of preparing a metal powder and a sintering aid powder, a step of mixing these powders into a mixed powder, a step of forming the mixed powder into a molded body, It is prepared by a method of sintering the formed body in an atmosphere surrounded by nitrogen to form a metal nitride sintered body. The closed pores are obtained by hollowing out the metal silicon powder. The ratio of the relative density to the closed pores in the whole pores can be controlled by the particle size of the metal silicon powder as the starting material. The metal silicon powder can be a commercially available high-purity metal. Powder, however, on the surface of metal silicon, a thermal oxide film is formed by a natural oxide film or subsequent heat treatment. The degree of cavitation of the oxide film is significantly changed due to the significant change in the amount of oxygen in the metal silicon powder. Or it is very important to control the composition of the grain boundary phase with this amount of oxygen. The amount of oxygen, converted into metal oxide (Si〇2), is preferably selected in the range of 0.2 mole% or more and 1.0 mole% or less. In addition, although the increase in the amount of oxygen in the mixing can be controlled by adding a coupling agent or the like, or it is important to suppress the increase in the amount of oxygen by adding a phenol lipid reducing agent or the like. The average particle size of the metal powder is 0.1 micrometer or more and less than 15 micrometers. If it is less than 0.1 m, the specific surface area becomes large, and the above-mentioned control of the amount of oxygen becomes difficult. Moreover, when it is 15 micrometers or more, since it becomes completely hollow, the reaction time becomes long, which is uneconomical. 0C2321 _8- This paper size applies to China National Standard (CNS) A4 specification (210X297 mm) 593209

As the sintering aid in the above-mentioned metal stone powder, a compound containing at least one kind of oxide, oxynitride cutting compound, etc. is preferably added as the oxide of Yb or Sm. The added amount is It is appropriate that the metal silicon powder is " more than Mohr% and more than 2.5 Mohr%. When it is less than 0.2 Molar%, the diffusion of metallic silicon cannot be promoted, and cavitation in the silicon particles cannot be fully performed, and at 2.5 Molar% In the above case, the total porosity is liable to decrease—ferrous oxide or aluminum oxide is known to the known metal silicon nitriding accelerator. In the case of the present invention, cavitation cannot be performed sufficiently, which is not good. In addition, the average particle diameter of the sintering additive added is preferably from 0.01 μm to 1 μm. When the average particle diameter is less than 0 μm, aggregation is likely to occur, which makes it difficult to handle. When it is 1 μm or more, It becomes difficult to carry out the nitriding reaction of the metal powder, and the surface oxide film of the metal powder may hinder the reaction. The above-mentioned sintering aid is added, and it is preferable to use an alkali metal or an alkaline earth metal or an oxide of these metals. It is added for the second sintering aid, and the addition amount of the second sintering aid is preferably 0.1 mol% or more and 15 mol% or less. The average particle diameter is 0.1 micrometer or more and 2 micrometers or less. Better. The metal silicon powder and the sintering auxiliary agent and the necessary corresponding organic adhesive are added by a method such as ball milling or ultrasonic mixing. After mixing, it is dried. After that, a predetermined shape can be formed to obtain a formed body. Generally, a known forming method such as a dry press forming method, an extrusion forming method, a doctor blade forming method, and an injection forming method can be selected for forming. The most desirable molding method mentioned above, in which the pre-mixed mixed powder is granulated in the shape of the molding, can increase the bulk density in advance, and improve the moldability. The above organic adhesive is added in the case of further improving the formability; C2322 -9-This paper size applies the Chinese National Standard (CNS) A4 specification (210 x 297 mm)

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k 593209 A7 B7 V. INTRODUCTION OF THE INVENTION Add 0. The above shaped body is heat-treated in an atmosphere surrounded by a nitrogen-containing gas to form a specific grain boundary layer. When the nitriding reaction of metal silicon is performed, each metal silicon powder is hollow. At the same time, the adjacent metal silicon powder nitrides are integrated into the reaction, and fine porous silicon nitride ceramics with closed pores can be obtained. The heat treatment is to perform a pretreatment and a cavitation reaction in order to form a specific grain boundary phase. Stage 2 of the process. The pretreatment can be performed in a carbon heating furnace, and the above-mentioned formed body is at a temperature of 800 ° C or higher and less than 1,000. (: The heat treatment is performed for more than 1 hour at the temperature. The surrounding gas during the heat treatment is an envelope gas containing 20% by volume or more of an inert gas. In the previous treatment, Yb, Sm, or Er is represented by RE, and it is necessary to form RE1. () The grain boundary phase shown by N2 (Si〇4) 6 or RE4Si2N207. In the case where such a grain boundary phase is not formed, the cavitation in the silicon particles will not be promoted in the subsequent reaction treatment. The porous nitrogen of the present invention Siliconized ceramics are difficult to produce. Therefore, in order to form such a grain boundary phase, the composition of the sintering aid, the amount of oxygen in the raw material powder, or the heat treatment conditions are adjusted. When the temperature of the pretreatment is less than 80000, no formation occurs. The above grain boundary phase. At temperatures above 1000 ° C, because the above-mentioned grain boundary phase is not sufficiently formed, the nitridation reaction of metal silicon starts, and it is difficult to obtain the desired porous silicon nitride ceramic, especially the grain boundary phase. RE10N2 (SiO4) 6 is preferred. The reaction treatment of the second-stage heat treatment is performed in an aerosol surrounded by nitrogen or ammonia containing more than 1,000, and in a surrounding aerosol, also in nitrogen or ammonia. You can add helium and heat Although a carbon heating furnace can also be used, the hollow structure is promoted for the diffusion of the metal powder, and the growth of the particles is suppressed. 10- r. Η n η ο ^ This paper size applies the Chinese National Standard (CNS) Α4 specification (210 X 297 mm) 593209 A7 B7 5. Invention description disappeared, it is better to use microwave or millimeter wave heat treatment, especially when heating with microwave radiation at a frequency above 20GHz, the metal nitrogen formed in the shell of metal silicon powder The compound (ShN4) can promote the diffusion of the metal, and the cavitation in the metal powder becomes easier, so it is better. The reaction treatment temperature is preferably 1000 ° c or higher, and the nitriding reaction of the metal powder is less than 10000t. Slow down, no economical, heating with carbon heating furnace below 1500 ° C, microwave heating below 175 (rc is preferred, above this temperature will produce metamorphic phases or particles of metal nitrides For growth, it is difficult to obtain the porous ceramics of the present invention after the cavitation structure is changed. In addition, it is better to increase the temperature from the uppermost temperature to the most two temperatures in two or more stages. Here, the metal Nitriding reaction is due to exothermic reaction. When the temperature is raised to the final sintering temperature, the exothermic temperature will exceed the melting point of the metal, which will cause the metal to melt. When the metal is melted, it will become an unreacted melting block. It will cause coarse pores or melt out of the formed body, which will cause the mechanical and electrical characteristics of porous ceramics to deteriorate. At the same time, usually, silicon metal becomes completely silicon nitride, and it will be done until the silicon metal disappears. Heat treatment for more than 2 hours, but depending on the purpose, it can be expected to shorten the heat treatment time, and silicon nitride ceramics with higher closed porosity can be obtained by the residual metal silicon. In the reaction treatment, the pattern is shown in Figures 3 and 4. First, the surface of the metal stone powder is nitrided. When the reaction process is performed, during the nitriding reaction, the metal diffuses to the periphery of the nitride, performs the nitriding reaction, and cavitation. To this end, there is finally a metal silicon powder. Partially becomes a hole, so the Chinese paper standard (CNS) A4 (2l0x 297 mm) is applied to the paper size of metal silicon

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593209

The diffusion of nitride in the peripheral portion is particularly remarkable in the case where the specific grain boundary layer is formed. The degree of hollowing depends on the amount of oxygen contained in the metallic silicon powder of the starting material, or the type of sintering aid or the heat treatment method. The size of each closed pore is basically based on the metallic silicon powder of the starting material. The size is determined by the particle size. If the particle size of the metal silicon powder is uniform, the size of closed pores will become uniform, and no coarse closed pores will be contained. At the same time, the pressure of the surrounding gas during the heat treatment is not limited, but it is preferably at least 1 atmosphere (10 kPa) and at most 5 atmospheres (507 kPa). Binding

The porous ceramic of the present invention obtained as described above is a hollow-dispersed structure having a uniform diameter by hollowing out each particle of the metal silicon powder. For this reason, it is a porous silicon nitride ceramic with excellent hygroscopicity resistance, low dielectric constant, and low dielectric loss. The relative density is less than 70%, and the closed-cell ratio in all pores becomes more than 50%. Furthermore, by selecting the average particle diameter, surface oxygen content, type of sintering aid, and sintering conditions of the raw metal silicon powder, the relative density can be made less than 50%, and the closed-pore ratio in the entire pores becomes more than 90%. In any section of the porous silicon nitride ceramic according to the present invention, as shown in FIG. 1, the radius of adjacent voids is set to ^, r2, and the thickness of the ceramic portion is set to b, which can be changed to (rl + r2) / b > 1, in short, the average particle diameter of the raw metal silicon powder, the amount of surface oxygen, the type of sintering aid, and sintering conditions can be selected. The diameter of the pores is equal to or greater than the thickness of the ceramic, preferably (^ + r2) / b > 2. With such an organization, the dielectric loss can be further reduced. The porous silicon nitride ceramic according to the present invention has a dielectric loss of about 10-4 or less in a desired form. As a mechanical property, the flexural strength of 3-point bending is above 200MPa, which has excellent electrical and mechanical properties.

593209

Porous silicon nitride ceramic. Example 1 An Er203 powder and an sintering aid having an average particle diameter of 1 // work n and an average particle diameter of 0.8 // m are prepared, which is equivalent to 0.8 mol% of silicon powder. Any kind of powder is a commercial product. Also, the surface oxygen content of Shi Xiling and Shi wy at the end of preparation is: melting of inert gas, and outside line; measured by the method of conversion, converted to training 2 and confirmed in advance. Seoul%. The prepared powders were dissolved in ethanol, and mixed with a ball mixer for 24 hours. At this time, as the oxidation inhibitor, 4 Wt% of octyl triethoxy stone evening courtyard was added. After mixing, it was naturally dried to make a dry type. Pressed to form a shaped body with a diameter of 23mm, a height of 3mm and a height of 4.5mm, a width of 7mm, and a height of 45mm. This formed body was heated in a nitrogen-enclosed gas (30 vol% Ar-70 vol / l) containing 30 vol.% Of argon at atmospheric pressure. NO was heated by a microwave having a frequency of 28 GHz and maintained at 95 C for 1 hour. After that, After the surrounding gas is made into a nitrogen surrounding gas at atmospheric pressure, the reaction treatment is performed under the conditions shown in Table 1. Here, 12000 * 3 + 1400 * 3 means that the temperature is increased to 1400 ° C after being held at 1200 ° C for 3 hours. The meaning of maintaining for 3 hours, the reason for the temperature rise in 2 stages is the nitriding reaction of polysiloxane, at 1400 ° (: the reason is the exothermic reaction (3 丨 + 2/3 1 ^ 2 = 1/3 51 to 4 + 641 ^ ) When the temperature rises to 1400 ° C all of a sudden, due to its own heating, the temperature will rise above 1400 ° C, and silicon will melt. After natural cooling, use a diameter of 20mm, a height of 1mm, a length of 3mm, a width of 4mm, The peripheral grinding disc and the flat grinding disc are final processed outside the height of 40mm, and the characteristics are measured as follows using the final processed sintered body. At the same time, the sintered body was refracted by X-rays, and it was confirmed that metal silicon did not remain. Into Si3N4.

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-13- The size of this paper applies to Chinese National Standard (CNS) A4 (210 X 297 mm) 593209 5. Description of the invention (A7 B7

The total porosity is the apparent density calculated from the size and weight of the sintered body, and the theoretical density is calculated from the mixing rule of the amount of sintering aid added. It is calculated according to the following formula: (Appearance density / theoretical density) X 100 (% ) The closed stomata ratio is measured by a mercury porosimeter and the open stomata volume is calculated by the following formula. (Total pore volume-Open pore volume) / Total pore volume X i 〇 (%) Adjacent void radii Γ1, Γ2, and thickness of ceramic part b are, the sintered body is cut, the cross section is ground, and SEM is used. Observed. Based on this SEM photograph, the center of gravity of the center point of the hollow hole was broken in two dimensions as shown in FIG. 1. The center points of adjacent adjacent holes were arbitrarily connected, and the radius rl, r2 of the hole and the thickness b of the ceramic part were measured. The average of the results at 50 points is shown in Table 1. As the electrical characteristics, the dielectric constant and dielectric loss (tan5) at 30 GHz were measured according to the measurement method specified in JIS R 1627. The results are shown in Table 1. Table 1

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No Sintering conditions Total porosity (%) Closed porosity (%) (rl + r2) / b Dielectric ratio tan δ (ΧΙΟ · 5) 1 1200 * 3 + 1400 * 3 80 92 2.43 2.1 12 2 1300 * 3 + 1500 * 3 80 90 2.40 2.1 7 3 1300 * 3 + 1600 * 3 75 88 2.01 2.9 9 4 1300 * 3 + 1650 * 3 31 Ί 70 2.0 5 35 5 * 1300 * 3 + 1700 * 3 28 51 1.4 6.8 90 6 * 1300 * 3 + 1800 * 3 29 35 1.20 7.5 100 -14-

0C032? ________ This paper size applies the Chinese National Standard (CNS) A4 specification (210X 297 mm) 593209 5. Description of the invention (12 * indicates a comparative example from the table 丨 It can be seen that the porous nitriding dream of the present invention has a porosity of 3 〇% or more, that is, the relative density is less than 70%. The ratio of closed pores is more than 50%. The porous nitrogen cut m made in this way is defined as electrical resistance, especially the dielectric loss characteristic is excellent, and the sintering temperature. For the case of 18G (rc, depending on the particle growth and phase transition, the structure of the cavitation is changed and detailed ^. The sintering temperature is 1200t ~ 1650 ° C '(rl + r2) / b value is above 2, dielectric loss It is an excellent product below 12 X 10-5. Example 2 A silicon powder having an average particle diameter of 1 / zm and a rare earth oxide as described in Table 2 as an sintering aid with an average particle diameter of 0.8 // m are prepared. The amount of silicon powder is equivalent to 0.88 ^ γ of silicon powder. Any powder is a commercially available product, and the surface oxygen of the silicon powder is prepared by melting the inert gas and measuring with an infrared detection method. It is confirmed that there is 0.7 mole%. Each powder prepared is carried out in the same manner as in Example 丨. After that, the surrounding gas is made into a nitrogen surrounding gas at atmospheric pressure, and then the temperature is raised to 1000 ° C for 3 hours, and then the temperature is increased to ^ ⑽, and it is maintained for 3 hours. After natural cooling, the same as in Example 1 is performed. During processing, the total porosity, closed porosity, specific permittivity, and dielectric loss of each sintered body were measured in the same manner as in Example 1. Also, as a mechanical property, a shape of a strength test piece was prepared in accordance with JIS Rl601, 3 The point bending strength was measured based on the same regulations, and the results of these measurements are shown in Table 2. At the same time, each sintered body was confirmed by χ-ray refraction to know that the metal silicon does not remain 'all changed to Si3N4. This paper scale applies Chinese national standards ( CNS) A4 specification (21 × 297 mm) 593209 A7 B7 V. Description of the invention (Table 2

No Type of sintering additive Total porosity (%) Closed porosity ratio (%) (rl + r2) / b tan 5 (x 10'5) Dielectric flexural strength (MPa) 7 * La) 〇i 58 10 0 120 4.5 40 8 * Nd, 〇i 59 20 0.54 110 4.2 TV / 50 9 Sin ^ O ^ 88 98 2.2 5 1.8_ 300 10 Er20 ^ 80 90 1.8 20 3.0 200 11 * Gd20 ^ 65 45 1.2 70 4.1 190 12 Yl > 2〇3 78 99 2.61 6 2.5 300 13 * A120 ^ 28 2 0 320 6.8 60 14 * Fe2 0 3 38 < 1 0 400 6.5 50 shows a comparative example. As can be seen from Table 2, the sintered body obtained by adding a sintering aid according to the present invention Yes, the porosity is above 70%, that is, the relative density is below 30%, the ratio of closed pores is above 50%, and the dielectric loss is as low as 2 X 104 compared with the conventional porous ceramics. The strength is 200 MPa or more, and it has excellent electrical and mechanical characteristics. In addition, although the value of (rl + r2) / b is 1 or more, if a sintering aid is selected, 2 or more can become a porous silicon nitride ceramic having a diameter of pores that is twice or more the thickness of the ceramic portion. The diameter of the hole is, for example, 0 · 7 // m in the sample No. 9 when the helium measuring machine is used. When the leakage is measured, the leakage is 8 X 1 (T9 atm) in the sample of n 〇9. .cc / sec, No 10 sample is 7 X 1 (T7, No 12 sample is 5 X 1 (T9, it is judged to have air-tight effect. CC0329 -16- Applicable to China National Standard (CNS) Α4 specification ( 210 X 297 mm y V. Description of the invention (14) Example 3 Thousand m τ Smart particle size 0 8 / ym ^ VK η Wuhe is used as a sintering aid, and the average particle size of Yb203 is equivalent to the silicon powder market Sales, X, preparation Shi Xi Yugu 4 dry cooking seeds and private matter were measured by the method, the oxygen content of the conversion surface is' as in Example 1 the same way 2 the same method into G.7 Moire%. It was mixed, shaped, heat-treated, and finally processed with the method of Example A. The total porosity and air-closing method of the obtained concrete body were measured. The results are shown in Table 3;

From Table 3, it can be seen that 'the amount of the sintering additive added is less than 0% and then 1%, and if it exceeds 2.5%, it is determined that the ratio of closed pores becomes low and the dielectric loss becomes large. In short, when the amount of the sintering additive is small, the cavitation in the dream particles cannot be sufficiently progressed, and because the particles grow, the ratio of closed pores decreases. Example 4 Each stone powder having an average particle diameter of 0.8H 'and Sm2O3', which is an average particle diameter of 0.8 as a sintering aid, are prepared as the crushed powder. The amount of oxygen on the surface of each Shi Xi powder was measured by the same method as described in Implementation #u.

-17- This paper size is in accordance with Chinese National Standard (CNS) A4 specification (210X 297mm) 5. Description of the invention (15) (change to 3120) As shown in Table 4, each powder For commercial products, using these powders 1 and _2, the same method is used to carry out ⑤combination and hot forming after processing. However, when the N ° 22 sample was mixed by ball milling, oxidized P,... Were added: the total porosity and closed porosity of each sintered body were measured in the same manner as in W. The results are shown in Table 4. Table 4 also shows the boundary grain phase with X-ray refraction. Table 4

No Particle size (/ m) Surface oxygen content (mol%) Total porosity (%) Closed porosity ratio (%) Grain boundary phase 19 * 10 --- ^ 0.17 65 ------ 21 SmSiN02 20 4 0.5 82 92 SminN ^ CSiOA 21 1 0.9 72 99 SiruSi9N, 〇7 22 * 1 0.9 52 45 Sm2Si3N40 ^ 23 * 0.8 3.0 40 10 Sm ^ Si ^ N ^ O ^ * ^ iU A * /. It shows that the comparative example uses the same raw material. When crushed powders of Ng 21 and Ng 22 were tested, the oxygen content of metal silicon powder after mixing with ball miu (ball mill) was increased to 1.7 mol% due to the addition of an oxidation inhibitor. According to Table 4, it can be determined that when the oxygen content of the metal hair powder is less than 0.2 mol% or more than 1.0 mol%, the composition of the grain boundary phase and the composition of the grain boundary phase for the purpose of the present invention are different because of the different composition. Decreased, closed stomata ratio becomes lower. These are considered to be due to different grain boundary phase composition, so the reaction morphology becomes different, and will not promote cavitation in metal stones. CC9331 -18_ This paper is suitable as $ ： as Standard (CNS) A4 specification (21Q χ 297 directors) 593209 A7 B7 V. Description of the invention (16) Example 5 The same silicon powder and Εγ203 powder as in Example 1 were prepared, and these powders were used in accordance with the examples. 1 The same method, mixing and molding. After holding at 950 ° C for 1 hour in the same manner as in Example 1, the formed body was heated under a carbon dioxide atmosphere at atmospheric pressure, heated with a carbon heater, and sintered under the conditions shown in Table 5. At the same time, the sintering conditions were the same as those described in Example 1. The final decoration process was performed as in Example 1. The total porosity, closed porosity, (rl + r2) / b value, and dielectric loss of each sintered body were measured in the same manner as in Example 1. The results are shown in Table 5. Show. The value of (r 1 + r2) / b is an average value measured at 50 places.

Table 5 No Sintering conditions Total porosity (%) Closed porosity ratio (%) (rl + r2) / b tan δ (χ ίο-5) 24 1300 * 3 + 1500 * 3 50 65 1.2 100 25 1000 * 3 + 1200 * 3 55 70 1.8 80 26 * 1300 * 3 + 1800 * 3 15 30 0.54 160 * indicates the comparison example

It can be seen from Table 5 that when the sintering temperature is 1800 ° C, the structure of cavitation changes and becomes dense due to grain growth and phase transformation. In addition, when Table 1 and Table 5 are compared, it can be seen that the one heated by the microwave closes the pores. The higher the ratio, the lower the dielectric loss. Here, one of the microwaves is efficient, and because it can be heated, it is considered that the metal silicon case (silicon nitride) is promoted by a diffusion reaction. Effect of the invention The paper size is in accordance with Chinese National Standard (CNS) A4 (210 X 297 mm) 593209 A7 B7 5. Description of the invention (17) According to the invention, compared with other materials, it is also consistent with the conventional method Ratio, a porous silicon nitride ceramic with a high closed pore ratio and uniformly dispersed closed pores can be obtained. The porous silicon nitride ceramic of the present invention has high closed pore ratio and excellent electrical and mechanical characteristics, so it can meet the requirements. Moisture resistance, low dielectric constant, low dielectric loss, and mechanical strength are also required for electronic circuit substrates, etc., which can exhibit excellent characteristics. This paper size applies to China National Standard (CNS) A4 (210 X 297 mm)

Claims (1)

593209 No. 091103295 Patent Application 92. 12.- Replacement of Tibetan patent application scope (Yueyi patent application scope in 1992 1. A porous silicon nitride ceramic, characterized by: relative density less than 70%, in all pores The ratio of closed pores is 50% or more; in any section, the radii rl, r2 of two adjacent pores and the width b of the ceramic portion have a relationship of (rl + r2) / b> 丨; and Contains the crystal phase of oxynitride or silicon oxynitride compound represented by REJizN ^ 7 or REiGN2 (Si〇4), where the rule is λ13, Sm * Er. 2 · —a silicon nitride ceramic circuit substrate, its characteristics The insulating layer, which is at least a part, includes the porous silicon nitride ceramic material as described in item 丨 of the patent application scope. 3. A method for producing porous silicon nitride ceramics, which is characterized in that a metal silicon powder and an equivalent metal are contained. Silicon powder 0 2 to 2 5 mol% of at least one of Yb, Sm, or Er compound powder, after forming into a shaped body, heat treatment in a surrounding aerosol containing nitrogen. 4. Porosity such as item 3 of the scope of patent application Of high quality silicon nitride ceramics by using microwave Or the above-mentioned molded body is heat-treated under millimeter wave irradiation to obtain a porous silicon nitride ceramic containing hollow ceramic nitride ceramic particles.